Title : Mount a folder on another folder Author: Solène Date : 22 May 2018 Tags : openbsd66 openbsd This article will explain quickly how to bind a folder to access it from another path. It can be useful to give access to a specific folder from a chroot without moving or duplicating the data into the chroot. Real world example: "I want to be able to access my 100GB folder /home/my_data/ from my httpd web server chrooted in /var/www/". The trick on OpenBSD is to use NFS on localhost. It's pretty simple. # rcctl enable portmap nfsd mountd # echo "/home/my_data -network=127.0.0.1 -mask=255.255.255.255" > /etc/exports # rcctl start portmap nfsd mountd The order is really important. You can check that the folder is available through NFS with the following command: $ showmount -e Exports list on localhost: /home/my_data 127.0.0.1 If you don't have any line after "Exports list on localhost:", you should kill mountd with `pkill -9 mountd` and start mountd again. I experienced it twice when starting all the daemons from the same commands but I'm not able to reproduce it. By the way, **mountd** only supports reload. If you modify */etc/exports*, you only need to reload **mountd** using `rcctl reload mountd`. Once you have check that everything was alright, you can mount the exported folder on another folder with the command: # mount localhost:/home/my_data /var/www/htdocs/my_data You can add `-ro` parameter in the */etc/exports* file on the export line if you want it to be read-only where you mount it. Note: On FreeBSD/DragonflyBSD, you can use `mount_nullfs /from /to`, there is no need to setup a local NFS server. And on Linux you can use `mount --bind /from /to` and some others ways that I won't cover here.